1. Field of the Invention
The present invention relates to MOSFET sensors, filters and nanostructures.
2. Description of the Prior Art
A problem with many conventional nano-sized chemical sensors is that they do not have a high specificity for particular chemical species to be detected. For example, MOSFETs, or more precisely, ISFETs (Ion Sensitive Field Effect Transistors), may be provided with porous gates to allow the environmental gases to arrive at the gate/dielectric interface and modify the threshold voltage and current voltage character. In fact, these ISFETs are often quite sensitive to gaseous ambients of different types. However, the electrical behavior of the ISFET does not generally allow different gases to be distinguished from each other, especially when there are several gases present in the environment simultaneously.
Similar to the problems faced in producing high specificity nano-sized chemical sensors, there is also currently no good way to produce very high flow-through nano-sized reaction chambers or chemical filters having a high degree of chemical specificity. For example, people having an oxygen deficiency often carry around a bulky oxygen tank which must be refilled on a regular basis. A lightweight active filter that allowed the passage of oxygen and very little nitrogen and larger dust and pollen particles would be a significant adjunct to the quality of life for many people
The present methods of electron beam lithography being developed at great expense may reach an ultimate minimum dimension of about 35 nm, which is indeed a large improvement over the 180 nm now being produced in the IC business. One of the best developed methods in this family is called SCALPEL (SCattering with Angular Limitation Projection Electron-beam Lithography). This system requires magnetic lenses, very thin masks, difficult mask alignment tools, and is quite complex. It appears to have significant promise in high throughput lithography for minimum dimensions down to about 35 nm, but not for smaller dimensions. A simple contact mask for e-beam lithography producing dimensions in the range of 1 to 5 nm would be of major benefit for a wide range of applications.